A prior art foot switch of the kind as herein referred is described in U.S. Pat. No. 4,114,275. The foot switch is designed as a relatively flat body which has a circular base plate for supporting the foot switch on the floor at a location close to a dental apparatus. A diaphragm is fixedly connected with the base plate in a fluid-tight manner for providing a hollow which serves as a pneumatic pressure chamber of a variable volume. The diaphragm is covered with a circular cover plate which is relatively moveable to the base plate and biased upwardly by a central pressure spring. By depressing the cover plate the hollow which is surrounded by the diaphragm will be reduced in size against the biasing force of the pressure spring. A pneumatic pressure signal is thereby produced which is transmitted by a signalling line to pneumatic switch valves of the dental apparatus for providing different functional control signals for controlling different functional members of the dental apparatus. The functional members could also comprise an electronic control circuit which is pneumatically actuated with an input switch.
German Patent Application published in DE 31 05 875 A1 discloses a box-shaped foot switch which comprises four pedals that are moveable relatively to a rectangular base plate and arranged in pairs of different size for selectively controlling to dental instruments and adjustable members of a patients chair. The pedals are connected via a logical circuit with a control circuit for the instruments and with a further control circuit for the adjustable members of the patients chair . The box shape of the foot switch results in a minimal trip safety and provides an unfavourable accessibility of the pedals which are arranged in pairs side-by-side so that the actuation of the same is not optimized.